1. Field of the Invention
The invention disclosed and claimed herein generally pertains to apparatus for improving performance of a tape transducer positioning mechanism, used in connection with a tape head designed to exchange data with magnetic tape media. More particularly, the invention pertains to apparatus of the above type wherein the tape transducer positioning mechanism is moved along a linear path of travel with respect to the tape, and the apparatus includes spaced apart magnetic components that produce a magnetic field orthogonal to the path of travel. Even more particularly, the invention pertains to apparatus of the above type wherein the orthogonal magnetic field is used to simultaneously perform different tasks, such as preloading the bearings of a transducer carrier, and at the same time suppressing a stray magnetic field proximate to the transducer.
2. Description of the Related Art
In a common data storage arrangement using magnetic tape, it is necessary to move a transducer such as a read/write head to different positions with respect to the tape. More particularly, the tape head, which is provided to selectively read data from and write data onto the tape, may need to be moved laterally across the width of the data storage tape. This may be necessary to place the head in operative relationship with any of two or more data bands or tracks positioned along the tape length.
In view of the above requirements, tape head actuators or positioning mechanisms have been developed, to move the tape head from one band to the other. Some of these actuators have two modes of operation, a first mode for moving the tape head between bands, and a second mode for maintaining alignment between the head and a particular track within a band.
In a common arrangement of the above type, the tape head is fixably mounted to an inner carriage. The inner carriage, in turn, is supported in an outer carriage for linear movement. A linear drive motor proximate to the inner and outer carriages is operable to linearly move the inner carriage, relative to the outer carriage, to position the tape head with respect to different tape bands. The outer carriage is mounted in a rigid frame by means of flexible brackets or the like. This enables the tape head and tape holding configuration to maintain alignment between the tape head and a particular tape track, notwithstanding vibrations caused by movements of the magnetic tape.
In the above tape head actuator arrangement, guide rails in conjunction with guide bearings or bushings are commonly used, to guide linear movements of the inner carriage and tape head. In order to minimize out-of-plane head movements when using this technique for head guiding, designs typically implement a method for preloading the guiding components, to remove play from the assembly. The most common method of preloading is by means of compression or leaf springs. However, these mechanisms tend to be plagued with reliability and performance problems. The performance problems typically result from such things as component fatigue, component wear, and unpredictable frictional forces at preload component interfaces. These are major contributors to poor assembly-to-assembly performance repeatability, and may eventually result in guiding failure.
A further problem encountered in tape head positioning actuators of the above type is the presence of stray magnetic fields. It will be readily apparent that controlling magnetic fields at the head/tape interface is essential, in order to accurately read and write data in tape drives. As a result, reducing external stray magnetic fields around the recording head is critical to proper read/write functionality. Stray fields around the head can potentially come from a number of sources, but most commonly are generated by linear drive or voice coil motors that are used to position the recording head relative to the tape. Placing high permeability materials between recording heads and voice coil motors (or other stray field generators) is a common technique utilized in an effort to shield heads from stray magnetic fields. However, in order to effectively protect the recording head from external stray fields, these shields must often be very large. In designs where space is limited and/or total allowable mass constraints have been imposed, these traditional shielding techniques can be difficult or impossible to implement.
In view of the above considerations, it would clearly be beneficial to provide a tape head positioning mechanism with an improved bearing preload arrangement, as well as with an alternate technique for reducing external stray magnetic fields around the recording head. It would be of further benefit if a single device or apparatus could be provided that would achieve both of these objectives.